Cardiac Tamponade and Pneumonitis as Indicators of Systemic Cobaltosis in Metal-on-Polyethylene Hip Implants

BACKGROUND Cobalt toxicity is a potential complication after metal-on-metal (MoM) prosthetic joint replacement but can also occur after non-MoM implant. Cobaltosis affects predominantly cardiovascular, endocrine, and neurological systems. We report a case of systemic cobaltosis with atypical presentation affecting predominantly the respiratory system in a patient who underwent hip replacement with metal-on-polyethylene (MoP) implant for a broken ceramic prosthesis. CASE REPORT A 35-year-old man with MoP implanted for a fractured ceramic prosthesis 1 year previously presented with pericardial effusion and pneumonitis. In the months preceding the admission, he was diagnosed with primary hypothyroidism, hearing impairment, and weight loss. During the diagnostic work-up his general condition deteriorated suddenly, with severe respiratory failure and subsequent cardiac arrest followed by an unsuccessful resuscitation. The autopsy showed pneumonitis with multifocal necrotic and inflammatory changes, dilated cardiomyopathy, metallosis surrounding the hip prosthesis, the loss of metal head sphericity, and multiple embedded ceramic particles in the polyethylene liner. His serum cobalt level was significantly elevated, confirming the diagnosis of systemic cobaltosis. CONCLUSIONS Pneumonitis in the course of systemic cobaltosis after hip replacement is not a widely recognized entity. The atypical multisystemic presentation misled the diagnostic process. The mechanism of third body wear by retained ceramic particles was responsible for the severity and the subacute course of the disease, related to the higher rate of cobalt release than in chronic MoM prosthesis wear.